Metal deactivators have been used for many years to inhibit metal corrosion. They are especially useful in lubricating oils to prevent sulfur induced corrosion of copper and copper alloys such as copper-lead bearings. One useful additive of this type is described in U.S. Pat. No. 2,719,125 wherein 1,3,4-thiadiazole 2,5-bis(alkyldisulfides) are made by reacting 2,5-dimercapto-1,3-4-thiadiazole (DMTD) with sulfenyl chloride or chlorine to form a di-sulfenylchloride intermediate which is reacted with a primary or tertiary mercaptan. Alternatively, the additives can be made by reacting DMTD with mercaptan and sulfur in a 1:1:1 molar ratio.
The preparation of various derivatives of DMTD is described in E. K. Fields "Industrial and Engineering Chemistry" 49 p. 1361-4 (Sept. 1957).
A method of making 2,5-bis(alkyldithio)-1,3,4-thiadiazole is disclosed in U.S. Pat. No. 3,087,932. This process involves the reaction of hydrogen peroxide with a mixture of DMTD or its alkali metal salt and an alkyl mercaptan.
U.S. Pat. No. 3,663,561 describes 2-hydrocarbyldithio-1,3,4-thiadiazoles which are useful as metal deactivators. They are made by reacting equimole amounts of a hydrocarbyl mercaptan and DMTD or its alkali metal salt in the presence of an oxidizing agent such as a peroxide, a hypohalite or oxygen.
More recently, U.S. Pat. No. 4,097,387 describes DMTD derived metal deactivators made by reacting a sulfur halide with an olefin to form an intermediate which is reacted with an alkali metal salt of DMTD.